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34 Cards in this Set
- Front
- Back
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to what does glycerol-3-phosphate dehydrogenase transfer electrons?
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glycerol-3-phosphate dehydrogenase is on the outer face of IMM and transfers electrons directly to CoQ
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what are the two shuttle mechanisms by which cytosolic NADH from glycolysis is carried into mitochondria?
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malate-aspartate shuttle
glycerol phosphate shuttle |
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on what intermediate do all electrons end up?
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coenzyme Q
moves between complex 1 and complex 2 it is the mobile element |
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why are cytochromes named the way they are?
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named for the Heme they contain
(cytochrome a has heme a, cytochrome b has heme b, cytochrome c has heme c) |
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which type of heme is in hemoglobin?
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heme b
(iron protoporphyrin IX) |
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at what point in the electron transport chain does NADH become oxidized?
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complex I
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what is the function of complex I?
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transfers two electrons and two protons from NADH to FMN, then to CoQ via a series of Fe-S centers
coupled to 2 H+ pumped to inner membrane space per electron |
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what is the function of pumping protons out of the inner mitochondrial matrix?
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make a pH gradient across IMM, which can be used to drive ATP synthase
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what is the function of complex II?
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transfer electrons from FAD and succinate to CoQ via Fe-S centers
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what oxidative phosphorylation complex is more commonly called succinate dehydrogenase?
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complex II
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which electron transport complex is the only one that doesn't liberate sufficient energy to drive protons out of the inner mitochondrial matrix?
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complex II
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what is the function of complex III in electron transport?
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transfers electrons from CoQ through center to cytochrome c
pumps out two protons per electron |
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what is the function of complex IV in electron transport?
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transfers electrons from cytochrome c, through several steps, eventually to oxygen (four electrons are required to reduce O2 to H2O)
pumps four protons for every electron |
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what are the key issues in the flow of electrons through electron transport?
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NADH oxidized by CoQ at complex I
FADH2 oxidized by CoQ at complex II CoQ oxidized by cytochrome c at complex III cytochrome c oxidized by oxygen at complex IV protons are pumped at every complex except complex II |
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what inhibits NADH dehydrogenase (complex I)?
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rotenone
amytal (barbiturate) |
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what inhibits complex III?
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antimycin A (an antibiotic)
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what inhibits cytochrome oxidase (complex IV)?
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carbon monoxide
cyanide |
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what inhibits ATP synthase?
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oligomycin (a streptomyces antibiotic)
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what is the function of uncouplers?
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(e.g. 2,4-dinitrophenol or DNP)
discharge the proton gradient without inhibiting the flow of electrons or inhibiting complexes put holes in membranes so energy from chemiosmotic gradient is lost as heat rather than energy or ATP |
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what is the physiological function of brown adipose tissue?
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upon a hormonal trigger, uncouples electron transport from ATP synthesis to generate heat
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where is brown fat found in newborns?
why is it brown? |
found in neck and upper back
it is brown because it contains a lot of mitochondria |
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what protein triggers uncoupling in brown fat? how?
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thermogenin (aka uncoupling protein or UCP) acts as a pore to let protons back into the inner mitochondrial matrix without making ATP, when triggered by release of fatty acids
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describe the steps in the heat generation of brown adipocytes
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norepinephrine binds to beta-adrenergic receptor (GPCR)
g-protein activates adenylate cyclase adenylate cyclase converts ATP to cAMP cAMP activates PKA PKA phosphorylates hormone-sensitive lipase, which frees fatty acids fatty acids allosterically activate thermogenin to open protons flow into matrix and heat is generated |
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Kearns-Sayre syndrome
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mitochondrially inherited disorder derived exclusively from mother, caused by various mitochondrial deletions
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what are the symptoms of Kearns-Sayre syndrome?
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ophthalmoplegia
weakness ataxia pigmentary retinopathy loss of hearing dementia seizures hypertrophic and dilated cardiomyopathy cardiac conduction abnormalities impaired GI motility diabetes mellitus short stature renal dysfunction |
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Alpers disease
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mitochondrial disorder caused by dysfunctional mitochondrial DNA polymerase gamma
presents with psychomotor retardation, intractable epiplepsy and liver failure in infants |
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Friedreich ataxia
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trinucleotide repeat mitochondrial disorder caused by frataxin defect
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what is frataxin?
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protein which acts as iron donor in Fe-S cluster biogenesis
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what is the only mitochondrial disorder inherited strictly from the mother?
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Kearns-Sayre syndrome
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mitochondrial myopathy, encephalopathy, lactic acidosis and stroke (MELAS)
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mitochondrial disorder caused by defect in numerous mitochondrial and nuclear genes
characterized by encephalopathy (seizures, dementia), recurrent stroke-like episodes at young age, myopathy, and lactic acidosis also ataxia, deafness, pigmentary retinopathy and short stature in some patients |
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myoclonic epilepsy with ragged red fibers (MERFF)
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defect in numerous mitochondrial and nuclear genes
characterized by myoclonus, epilepsy, ataxia, and dementia |
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what is myoclonus?
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brief, involuntary twitching of a muscle or a group of muscles
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Leigh syndrome
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infantile onset mitochondrial disorder caused by various defective mitochondrial and nuclear genes
damages primarily the brainstem and basal ganglia causing hypotonia, ophthalmoplegia, nystagmus, and psychomotor regression mean age of death is 5 years |
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what is a hallmark of mitochondrial disorders?
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ragged red fibers
large abnormal mitochondria in myofibers occur in no other disease, but are only present in a third of mitochondrial disorders |
